Process and apparatus for cleaning coals and other materials



Dec. 6, 1938. F. TROMP 2,139,047

PROCESS AND APPARATUS FOR CLEANING GOALS AND OTHER MATERIALS Filed April 16, 1936 5 Sheets-Sheet 1 JNVENTOR= KLAA F TRUMP ATTORNEY K. F. TROMP Dec. 6, 1938.

PROCESS AND APPARATUS FOR CLEANING GOALS AND OTHER MATERIALS 3 SheetS-Sheet 2 Filed April 16, 1956 NEU.

AT'TORN EV Dec. 6, 1938. K. FTTROMP 2,139,047

PROCESS AND APPARATUS FOR CLEANING GOALS AND OTHER MATERIALS Filed April 16, 1936 3 Sheets-Sheet 3 Patented Dec. 6, 1938 UNITED STATES PROCESS AND APPARATUS FOR CLEANING GOALS AND- OTHER MATERIALS Klaas F. Tromp, Kerkrade, Netherlands Application April 16, 1936, Serial No. 74,650

In (lermany May 23, 1935 Claims. (01. zoo-1'13) uid and adapted to be used as the solid constitu ent ofthe suspension.

We are aware that for the wet cleaning of coals by means of a suspension several processes have already been suggested. In the Chance process, a mixture of sea sand or the like and water is used for causing the coal to float and the slate to sink therein. This fluidic mixture is mechanically agitated and, in' addition, a rising current of water is introduced near the bottom of the tank, said current being so strong that,

while the slate is allowed to sink, the sand is kept in suspension. It follows that it should be endeavoured to keep the density of the suspension approximately constant and uniform through- 'out practically the full height of the tank. In

practice, however, this cannot be accomplished.

Besides, this process can only be used for separating the coals into two products, so that the material sunk to the bottom must again be washed in order to avoid losses of valuable middlings.

Conklin has alreaiw drawn attention to the fact that the rising currents in the washing tank and also the agitation of the suspension may be omitted if the sand is very finely divided and has a particle size of say 0.1 mm. It is said that in this manner a very stable suspension can be obtained and that the latter preserves during a long time a uniform density throughout the tank. However, practically suflicient stability of the suspension requires such an extraordinary fineness of the sand as to render the process uneconomical. In practice it cannot be avoided that the 4.1 sand slowly settles, the consequence being that after some time'the density of the suspension gradually increases in downward direction, and that a certain amount of middlings, i. e. coal of intermediate ash content such as bony coal, re- .su mains suspended between the surface, irom which thelower gravity product is skimmed and the bottom, from which the heavy refuse is to be discharged. Stated in other language, there may gradually accumulate such a big amount of middlings in the intermediate layers 01 the suspension, that the heavy material is prevented from sinking to the bottom and the further separation is seriously interfered with.

It has also been suggested to use more or less colloidal substances for stabilizing the suspension, 5 but these substances increase the viscosity of the fluid and impair the settling of the heavy material so as to make the separation very imperfect. Besides, also this process naturally allows of a separation into two products only. 10

In accordance with my present invention, two or more layers with densities increasing in downward direction are allowed to form in the suspension in which, moreover, more or less horizontal currents are created for the purpose of carrying the floating and the suspended products towards individual discharge means.

The stratification can be created by allowing the sand to settle, i. e. by turning to advantage a phenomenon, which in known processes in the art 20 works out as an inconvenience and which, therefore, has always necessitated special measures for stabilizing the suspension.

A second method- 01 obtaining the desired stratiflcation is, supplying the washing tank with 26 suspensions of different densities.

It is pertinent here to remark that the word stratiflcation is not intended to convey the idea 01' distinct layers having diflerent densities, since the density 01' the body of fluid in the tank in- 30 creases very gradually in downward direction. This has the marked advantage that the middlings are distributed over the full depth and are not confined to one single sharply-defined layer, so that there is no danger of undue accumulation 85 of middlings, as is the case with the Chance process.

For further explanation, reference is had to the diagrammatic drawings, in which Figs. 1 and 2 illustrate vertical longitudinal sections 01' two 40 diilferent washing tanks in accordance with my invention, while Fig. 3 illustrates an entire plant installation including the form .of apparatus shown in Fig. 2. J In Fig. l, the tank I proper has vertical front 45 and rear walls, a substantially vertical left hand side wall-and a slanting right hand side wall. Mounted on the left hand side of the tank there ..is a bucket elevator 2 having its delivery end 3 located vertically above an inclined dewatering screen 4. Opposite this screen there are some sprayers 5, and mounted below the same there is a boot 6.

The upper portion of the slanting right hand side wall 0! the tank I is double. The lower end 68 of the interspace I thus formed freely communicates with the tank, whereas the closed upper end thereof is connected with a discharge pipe 8 provided with a stop-valve 9. A second pipe III serves for discharging the fluid flowing over the right hand side top edge II of the tank, whereas its scrapers extend to a certain depth into the suspension, but at some distance from the edge 'II said part begins to move upwards at a certain flow edge II, the run-of-mine'c'oal to be charged 55 angle. In parallel relation with this upwardly inclined part and at a small distance below the same there is provided a dewatering screen I8, the left hand side end of which is located somewhat below the level of the overflow edge II. The right hand side end of said screen meets the left hand side end of a downwardly inclined screen I9 mounted over the screen I4, and opposite the screen I9 there are provided some sprayers 20.

, The right hand side wall of the tank I guides the lower part of a second drag conveyor 2|. driven in clockwise direction and also provided with slotted or perforated scrapers. ,Th'e upwardly moving part of this conveyor ends vertically above the upper end of the screen I4. Intermediate the lower end of the conveyor 2| and the bottom of the tank I there is provided a partition 22 which, together with the inclined left hand side wall of the tank, defines a pocket 28 receiving the feed end of the bucket elevator 2.

Opening into the left hand side wall of the tank I there are three vertical, flat feed conduits 23. 24, 25, the width ofwhich is substantially equal to that of the tank I and-the discharge openings of which are turned to the right. The opening of the conduit 23 is situated about at the level of the overflow edge II, that of the conduit 24 about at the level of the opening of pipe I2, and that of conduit 25 about at the level of the-top edge of partition 22. v The described apparatus .operates as follows: Presuming the tank I to be filled with the desired suspension of sand in water upfto the overinto the tank as at A, i. e. on the left handside of the tank, and the drag conveyors I'I, 2| as' well as the bucket elevator 2 to be suitably driven, the pure coal will float and be carried by the lower part of the conveyor II towards the screen I8 and raked over the same so as to be lifted out of the fluid, whereupon-it slides down screen I9.

-'I'his coal is washed by the water from the sprayers 20; and the adhering suspension together with the washing water is collected by the boots I5, IS.

The liquid drained from tank I through pipe I0 is replaced by fluid from the conduit 23. Since this fluid flows in horizontal direction near the surface, it prevents thesetting up of undesired vertical currents, which otherwise could be created by the operation of the conveyor II.

(The slatesinks to the bottom and accumulates in the pocket 28, from which view of the fact that the sand is not prevented from settling and that as a consequence the suspension has adensity increasing in the direction from top to bottom, the middlings remain suspended at a greater or smaller depth. The fluid fed into the tank through the conduits 24 and 25 create currents from left to right intermediate the surface of thesuspension and the bottom of the tank, whereby'the suspended middlings are carried towards the drag conveyor 2I' and discharged thereby. The said currents also cause pure coal and middlings, which may be carried along by the sinking slate, to be separated therefrom.

The pipes 8 and I2 also discharge certain amounts of fluid from the tank I, said amounts being controlled by means of the stop valves 9 and I3 as conditions require.

The liquids discharged by the pipes III, -8 and I2 are returned to the tank I, if necessary after being purified (for instance by screens, froth flotation, etc.) and regenerated. According to requirements, the fluid from pipe, I0 may be returned through conduit 23, that from pipe I2 through conduit 24, and that from pipe 8 through conduit 25. Alternatively, the liquid from I2 may be returned to 25 (or to both 25 and 24), that from III to 24 (or to both 23 and 24), and stop valve 9 in pipe 8 kept closed. In this manner, upwardly inclined currents can be created in the tank, whereby the settling of the sand is counteracted.

The decrease of the density of the upper layer and the increase of the density of the bottom layer may be compensated by the fluids discharged fromthe tank being wholly or partly mixed with one another before being returned .to the tank. For instance, part of the suspen- If the aforesaid second method is used for obtaining the desired stratification, suspensions having increasing densities and stored in different reservoirs .may be fed to the washing tank through the conduits 23, 24, 25 and discharged through. the pipes III, I2 and 8, respectively. This is particularly useful when the sand is very finely divided, or when the suspension is excessively stabilized by impurities of the coals. If under these conditions one would rely exclusive- 1y upon the settling of the sand for the creation of the desired stratification, the horizontal currents of liquid would have to be so feeble that undue accumulation of middlings in the tank would be likely to occur and the settling of the slate'would thereby be impaired.

With the same object in view, the suspensions discharged as at III, I2 and 8 may be collected in a common storing vessel in which the solid matteris allowed tosettle to a certain extent, and from which the fluid is withdrawn at various levels, "that is to say with different densities, to be fed to the conduits 23, 24, 25.

The washing water from the boots 6 and I6 Y may be purified in any appropriate manner, for

. instance by froth flotation, or by screening of! the coarser particles (say over 0.15 mm.). Alternatively, the separation of the sand from the finest slurry and slates can also be accomplished by gravity concentration. This possibility of re-' moving the finest slurry and slates, which otherpension necessitates the employment of exceptionally flne sand, so that the slurry cannot possibly be separated therefrom, at least not without substantial loss of sand.

The settling of the sand can also be controlled by bubbling air through the suspension, if desired in conjunction with upwardly inclined currents of liquid.

It will be understood that the middlings may still be graded in accordance with their specific gravities, by providing the tank withtwo or more conveyors 2| at difierent levels.

If necessary, the suspension may be stabilized to a certain degree by means of colloidal substances. Preferably, high gravity material is employed as the solid constituent of the suspension, the nature of which depends upon the specific weights of the desired middlings'. If the range thereof is very wide, a relatively coarse suspension can suitably be used.

Instead of one single solid constituent of the suspension, a plurality of these constituents may be employed, the one being preferably very fine and the other somewhat coarser or heavier. This is of importance especially in those cases, wherein the coals to be dressed do not themselves contain a suflicient amount of stabilizing substances.

A suitable suspension consists of 50 parts by weight of sand (consisting of equal parts of very finely ground fluorspar and ground magnetite) and 50 parts by weight of water.

The apparatus shown in Fig. 1 has proved to operate satisfactorily under various conditions. Meanwhile, the fact that the substantially horizontal currents of liquid emanating from the inlet conduits 23, 24, are bound to follow deflnite and invariable paths with any given setting of the apparatus may have the result that the products kept in suspension intermediate the axes of said currents lag behind those suspended in said axes, or even remain stagnant. With a view to obtaining a more uniform transportation of said products towards the drag conveyors, Fig.

2 illustrates an improved apparatus, in which the openings through which fluid is fed to and discharged from the tank are adapted to be moved up and down. By these means each of said currents is enabled to sweep a zone of comparatively great depth and stagnancy of fluid is thus positively avoided throughout the tank.

Like reference numerals indicate like parts in all figures.

The construction of the tank shown in Fig. 2 does not differ essentially from that of the tank illustrated in Fig. I, so that it is not necessary-to describe the same in detail.

As shown, the drag conveyor I! may be passed either around a drum 23, or around a drum 21., according to whether coarse coals or fine coals are to be treated.

The fluid supply pipes 23, 24 and 25 open into chambers 29, and 3|, respectively, formed on the inner side of the left hand side wall of the tank I. A slide valve 32, which is movable up and down in parallelrelation with said side wall, forms the closure of these chambers and is provided with horizontal slots 33, 34, 35, through which said chambers communicate with the tank. The chambers 29-3|, the slide valve 32 and the slots 33-35 all extend through substantially the full width of the tank.

In the drawings, the slide valve 32 is shown nearly in its extreme lower position, with the slots 33, 34 and 35 located near the bottoms of their respective chambers 23, 30 and 3|.

Similarly, the discharge pipes 8, l2 and 36 open into chambers 38, 39 and 40, respectively, the

closure of which is formed by a second slide valve 4| having slots 42, 43 and 44, respectively.

During operation of this apparatus, the slide valves are slowly moved-up and down, either manually or by suitable mechanism, the result being that each of the three substantially horizontal currents of fluid created at different depths will sweep a zone defined by the extreme lower and upper positions of its inlet and outlet slots, so that the fluid is kept in movement throughout the depth of the tank and the suspended product is in its entirety transported towards the drag conveyor 2|.

Fig. 3 of the drawings diagrammatically illusstrates a completeplant, comprising, in addition I to a washing tanksubstantially as shown in Fig. 2, various auxiliaries for actuating the slide valves, for returning and, if desired, mixing the various suspensions withdrawn from the tank, for creating 'risingcurrents of fluid in the tank, etc. Since in g. 3 like parts serve the same purposes and. are designated by the same reference numerals as in Fig. 2, it is not necessary to, further describe the same. It will, however, be noted that the single flight conveyor 2| shown in Fig. 2 has been replaced in the plant of- Fig. 3, by two conveyors 2|a and 2|b mounted at different levels in the tank Accordingly, the screen l4 as per Fig. 2 has been substituted in Fig. 3 by two superposed screens Ha, Mb.

45 is a tank provided with a stirring device 46 a valve 41, with the suction side of a pump 50,

the discharge pipe 50b of which has a nozzle 5| extending across the width of the tank some distance vertically. above the funnel-shaped upper portion of conduit 23.

The discharge pipe I2 is connected with the suction side of a pump 43, the discharge pipe 43b of which has a similar nozzle 52 some distance vertically above the funnel-shaped upper portion of conduit 24. 1

Finally, the discharge pipe 8 is connected with the suction side of apump 48, the discharge pipe' 48%; of which has a'similar nozzle 53 some dis tance vertically above the funnel-shaped uppe portion of conduit 25.

In order that the suspensions discharged by conduits 43b and 50?) may be mixed in any desired proportion, an inclined board 54 is mounted intermediate the nozzle 5| and the funnel-shaped upper end of the conduit 23, so as to deflect the fluid discharged from nozzle 5| to the conduit 24. The length of said board is smaller than that of the nozzle 5| and-of theffunnel-shaped upper end of conduit 23, measured in a direction at right angles to the plane of the drawing,so that part of the'said fluid will be received by the conduit 23. Similarly, an "inclined board 55 of suitable length and disposed intermediate the nozzle 52 and the funnel-shapeduppe'r end of conduit 24 serves to deflect a predetermined portion of the fluid discharged by nozzle 52 to the conduit 23, the remainder flowing into the conduit 24.

As shown, pipe 48b has a branch pipe 66 opening into the bucket elevator 2 and provided with a valve 65, another valve 84 being-mounted in pipe 48b intermediate said branch and the nozzle 53. By suitably setting valves 64 and- 65, any desired proportion of the fluid suppliedby pipe 48b may thus be discharged, through said elelvator, near the bottom of tank I and create therein a rising current indicated by the arrow Air may be bubbled through the suspension by means of a compressed air pipe 61 having a number of branches 69, each provided with a valve 58 and opening into the bottom of the tank.

The means for actuating the slide valves 32 and 4| comprise racks 56 and 59 secured to extended portions of said valves, respectively, and adapted to be driven by pinions 51 and 60, respectively. Pinion 5'I is secured to a sprocket wheel BI and pinion 60 is secured to a sprocket wheel 62, a chain 58 being passed around said wheels, so that oscillatory movement imparted to wheel 6|, or 62, will cause the slide valves 32., 4| to be moved up and down.

Having now fully described my invention, what I claim is:

1. In a process for separating solid materials I having'diiferent specific gravities by means of a suspension of sand in liquid contained in a tank in which the density of the suspension increases from top to bottom, the steps which consist in feeding the materials to be separated into the bath at one side thereof, causing the heavier of said materials to settle in the bath, causing the lighter materials to fioat on the bath, causing the materials with an intermediate specific gravity to remain suspended in the bath, withdrawing limited quantities of suspension per unit of time below the top level of the bath at the side opposite the feed side and introducing limited quantities of the suspension per unit of time into said bath at the feed side thereof substantially at the withdrawal level'so as to create a slow substantially horizontal current in the bath and cause the material with an intermediate specific .fioating material and suspended material, and

simultaneously maintaining the portionof the bath-out of the direct path of said current in a substantially quiescent condition.

2. In a process according to claim 1, the step of mixing the withdrawn suspension with suspension withdrawn from another level of the bath prior to returning the same into the tank.

' stantially horizontal current-in the bath.

of and simultaneously withdrawing a commensurate amount of liquid suspension from the bath at the opposite side thereof at a level corresponding to the introductory level, whereby to createa slow substantially horizontal current from side to side of the bath while simultaneously maintaining the portion of the bath out of the direct path of said current in a substantially quiescent condition, to cause a portion of the materials having a certain specific gravity to be carried by said current from the feed side toward the discharge side of the bath and relative to another portion of said materials having a different specific gravity, and

removing the -material carried by said current from the bath at the discharge side thereof.

5. In a process for separating solid materials of varying specific gravities by means of a suspension of comminuted solids in a liquid bath contained in a tank in which the density of the suspension increases from top to bottom to form vertically spaced substantially horizontal zones of different specific gravities, the steps which consist in feeding the materials to be separated into the bath at one side thereof and permitting the same to respectively seek the zone levels corresponding to the specific gravities of the mate'- rials, separately introducing liquid suspension at vertically spaced levels at the feed side of the bath and substantially at the upper surfaces of said spaced zones 'of suspension and simultaneously withdrawing commensurate amounts of liquid suspension from the bath at the opposite side thereof at vertically spaced levels corresponding to the introductory levels, whereby to create vertically spaced slow substantially horizontal currents from side to side of the bath while simultaneously maintaining the portion of the bath out of the direct path of said currents in a substantially quiescent condition, to cause they materials of varying specific gravities to be carried by said currents from the feed side toward the discharge side of the bath, separately removing said materials from the bath at the discharge side thereof independently of the withdrawal of the current-creating liquid, and changing the elevation of the slow substantially horizontal currents relative to the bath level during movement of thematerials through the bath so as to more thoroughly traverse the zones through which said currents are horizontally directed.

6. In a process for separating solid materials of varying specific gravities by means ofa suspension of comminuted solids in a liquid bath contained in a tank in which the density of the suspension increases from top to bottom to'form vertically spaced substantially horizontal zones of different specific gravities, the steps which consist in feeding the materials to be separated into the bath at one side thereof and permitting the same to respectively seek the zone levels corresponding to the specific gravities of the materials, separately introducing liq'uid suspension at vertically spaced levels at the feed side of the bath and substantially at the upper surfaces of said spaced zones of suspension and simultaneously withdrawing commensurate amounts of liquid suspension from the bath at the opposite side thereof at vertically spaced levels corresponding to the introductory levels, whereby to create vertically spaced slowsubstantially horizontal currents from side to side of the bath while simultaneously maintaining the portion of the ,bath out of the direct path of said currents in a substantially quiescent condition, to cause the materials of varying specific gravities to be'carried by said currents from the feed side toward the discharge side ,of the bath, and separately removing said materials from the bath at the.

discharge side thereof independently of the withpension of comminuted solids in a liquid bath contained in a tank in which the density of the suspension increases irom top to bottom, the steps which consist in feeding the materials to be separated into the bath at one side thereof and permitting the same to respectively seek zone levels corresponding to the specific gravities of the materials, introducing liquid suspension at the feed side of the bath and simultaneously withdrawin a commensurate amount of suspension from the bath at the opposite side thereof at a level corresponding to the introductory level, whereby to create a slow substantially horizontal current from side to side of the bath while simultaneously maintaining the portion of the bath out of the direct path of said current in a substantially quiescent state, to cause a portion'of the-materials having a certain specific gravity to be carried by said current from the feed side toward the discharge side of the bath and relative to another portion of said materials having a difterent specific gravity, removing the material carried by said current from the bath at the discharge side thereof, and changing the elevation of the slow substantially horizontal current relative to the bath level during movement of the material through the bath so as to more thoroughly traverse the zone through which said current is horizontally directedc 8. Apparatus for separating solid materials having different specific gravities, comprising a tank for holding a body of suspension of comminuted solids in liquid, said tank having means associated therewith for removing material from the bottom thereof and means for removing material from the level of the suspension in the tank; means for feeding the materials to be separated into said tank at one side thereof to permit said materials to respectively seek zone levels corresponding to varying specific gravities of the materials, independent means for introducing liquid suspension at the feed side of the tank and for withdrawing liquid suspension therefrom at the opposite side thereof, said introducing and withdrawing means being respectively disposed at substantially the same level relative to the horizontal and below the level of the suspension in the tank, said liquid suspension introducing and withdrawing means serving to create a slow moving substantially horizontal current in said tank for conveying materials to be separated thereacross, means at the discharge side of the said tank for removing separated material therefrom, and means for transferring liquid suspension withdrawn from said tank to said liquid introducing means.

9. Apparatus according to claim 8, including means for imparting up and down movements to the means for introducing liquid suspension into the tank and to the means for withdrawing said suspension from the tank.

10. Apparatus according to claim 8, includin means for imparting up and down movements to the means for introducing liquid suspension into the tank and to the means for withdrawing said suspension from the tank, said movement imparting means including one or more individual chambers into which said suspension is respectively introduced and withdrawn, open ported slide valves mounted for up and down movement and separating said chambers from the tank, and means for imparting synchronized up and down movements to said slide valves.

KLAAS F. TROMP. 

